Glass composition to be used for manufacturing inorganic fiber, method of manufacturing the same and molded product of inorganic fiber

ABSTRACT

A glass composition improves the bio-solubility (solubility to physiological salt water), and is suitable for manufacturing inorganic fiber and a molded product of such inorganic fiber. The glass composition to be used for manufacturing inorganic fiber is characterized by containing SiO 2  by 52 to 72 wt %, Al 2 O 3  by less than 3 wt %, MgO by 0 to 7 wt %, CaO by 7.5 to 9.5 wt %, B 2 O 3  by 0 to 12 wt, BaO by 0 to 4 wt %, SrO by 0 to 3.5 wt %, Na 2 O by 10 to 20.5 wt %, K 2 O by 0.5 to 4.0 wt % and P 2 O 5  by 0 to 5 wt %. The raw material of the glass composition contains cathode ray tube glass and/or liquid crystal glass by 0 to 50 wt %.

FIELD OF THE INVENTION

This invention relates to a glass composition to be used formanufacturing inorganic fiber, a molded product of inorganic fibermanufactured by using such a glass composition, and a method ofmanufacturing such molded product.

BACKGROUND OF THE INVENTION

Molded product of inorganic fiber such as heat insulating materials madeof inorganic fiber, which may be glass fiber, glass wool, ceramic wool,rock wool or the like are being popularly used.

In recent years, it has been found that various diseases of respiratoryorgans may be triggered when dust of fiber is inhaled by men andaccumulated in the lungs. While the real cause of diseases of therespiratory system that are triggered by inorganic fiber such as ceramicwool, rock wool and glass wool is a complex one, the inorganic fiberinhaled to the lungs can be eliminated from the body if it is dissolvedto the body fluid in a short period of time, so that the diseases of therespiratory system caused by the fiber may be suppressed or dissolved.

Therefore, from the viewpoint of the influence of inorganic fiber to thehealth of human body, it is desirable to eliminate the inhaled dust ofinorganic fiber from the body before it gives rise to any harmful effectto the body by raising the solubility of the inorganic fiber to the bodyfluid. More specifically, inorganic fibers that show a high solubilityto physiological salt solutions (physiological salt water, or normalsaline solution) in a solubility test using such solutions instead ofbody fluid will be desirable.

Meanwhile, an index value called KI (Krebserzeugender Index) value thatis determined as carcinogenic index from the chemical composition ofinorganic fiber by means of an arithmetic formula has been adopted inplace of a solubility test by Germany and some other EU countries aspart of legal restrictions on dangerous substances in an effort forsuppressing the problem of inorganic fiber. The KI value is determinedby subtracting twice of the content (weight %) of aluminum oxides fromthe total sum of the contents (weight %) of oxides of sodium, potassium,calcium, magnesium, barium, boron and so on.

Inorganic fiber showing a high KI value as determined in a manner asdescribed above is assessed to be less carcinogenic, whereas inorganicfiber showing a low KI value is assessed to be highly carcinogenic. Morespecifically, inorganic fiber is assessed to be carcinogenic if it istaken in by a small amount and shows a KI value lower than 30, and iftaken in by a large amount and shows a KI value between 30 and 40,whereas inorganic fiber is assessed to be non-carcinogenic if it istaken in by a large amount and shows a KI value of 40 or more. However,it should be noted that the KI value is one of a number of currentlyavailable assessment techniques. Even if inorganic fiber shows a low KIvalue, the fiber shows a high solubility (bio-solubility) tophysiological salt water, such fiber may be easily eliminated from thehuman body and hence not harmful to the body, although the KI value isregarded as important when assessing the carcinogenicity of inorganicfiber.

Inorganic fiber for manufacturing molded inorganic fiber products suchas glass wool thermal insulators needs to be easily manufactured. Morespecifically, from the viewpoint of the properties of the inorganicfiber and the durability of the manufacturing facility, the glasssoftening point is preferably low, and the glass viscosity is also low.Additionally, from the viewpoint of the stability of the manufacturingfacility and that of operation, the liquidus temperature is preferablylow. While a high chemical durability of inorganic fiber per se isdesirable, a high chemical durability and a high bio-solubilitycontradict each other.

Furthermore, a vast amount of glass wastes produced from cathode raytubes of television sets and those of computer displays as well aswastes of liquid crystal glass are currently being produced to give riseto a serious problem of waste disposal. At the same time, such glasswastes are desired to be recycled from the viewpoint of effectiveutilization of resources.

Finally, since inorganic fiber and molded products of inorganic fiberare being manufactured on a mass production basis, it is desired tolower the manufacturing cost.

SUMMARY OF THE INVENTION

In view of the above identified circumstances, it is therefore an objectof the present invention to provide a glass composition suitably usedfor manufacturing inorganic fiber and molded products thereof, whichshows a high bio-solubility so that it may not exert any harmful effecton the human body. In other words, an object of the present invention isto provide a glass composition with both chemical durability andbio-solubility which contradict each other. Another object of thepresent invention is to provide a glass composition to be used formanufacturing inorganic fiber that does not adversely affect the humanbody and is suitable for manufacturing molded products at low cost byutilizing glass wastes of cathode ray tubes or liquid crystal glass forthe purpose of effective use of resources.

In an aspect of the present invention, the above objects are achieved byproviding a glass composition to be used for manufacturing inorganicfiber, containing SiO₂ by 52 to 72 wt %, Al₂O₃ by less than 3 wt %, MgOby 0 to 7 wt %, CaO by 7.5 to 9.5 wt %, B₂O₃ by 0 to 12 wt, BaO by 0 to4 wt %, SrO by 0 to 3.5 wt %, Na₂O by 10 to 20.5 wt %, K₂O by 0.5 to 4.0wt % and P₂O₅ by 0 to 5 wt %.

B₂O₃ may be essential, in other words, the glass composition may containB₂O₃ by 0.1 to 12 wt %.

B₂O₃, BaO and SrO may be essential. In other words, the glasscomposition may contain B₂O₃ by 0.1 to 12 wt %, BaO by 0.1 to 4.0 wt %,SrO by 0.1 to 3.5 wt %. If P₂O₅ is essential, it is desirable that aglass composition according to the invention contains P₂O₅ by 0.1 to 5wt %.

B₂O₃ may be essential. In other words, the glass composition may containB₂O₃ by 0.1 to 12 wt %, and has the KI value of 40 or more. The KI valueis obtained by formulaKI=(Na₂O+K₂O+CaO+MgO+BaO+B₂O₃)−2×Al₂O₃,where the molecular formulas represents the respective contentsexpressed by wt %.

No B₂O₃ may be contained, BaO and SrO may be essential. In other words,the glass composition may contain BaO by 0.1 to 4.0 wt % and SrO by 0.1to 3.5 wt %.

In another aspect of the invention, there is provided the glasscomposition which raw material of the glass composition contains cathoderay tube glass and/or liquid crystal glass by 0 to 50 wt %, preferably 8to 50 wt %.

In still another aspect of the invention, there is provided a method ofmanufacturing a molded product of inorganic fiber, comprising:

-   -   melting the glass composition according to one of claims 1-8 in        a melting furnace;    -   fining the molten glass composition into fine glass fiber in a        fiberizing apparatus;    -   blowing an adhesive agent (binder) to the glass fiber to provide        it with shape stability and load characteristics;    -   molding the glass fiber into the inorganic fiber molding having        a predetermined density and a predetermined thickness by means        of a fiber condenser and a dryer; and    -   subsequently cutting the molding to produce a finished product.

In still another aspect of the invention, there is provided a moldedproduct of inorganic fiber manufactured by the above-described method.

PREFERRED EMBODIMENTS OF THE INVENTION

A glass composition to be used for manufacturing inorganic fiberaccording to the invention contains SiO₂ by 52 to 72 wt %, Al₂O₃ by lessthan 3 wt %, MgO by 0 to 7 wt %, CaO by 7.5 to 9.5 wt %, B₂O₃ by 0 to 12wt, BaO by 0 to 4 wt %, SrO by 0 to 3.5 wt %, Na₂O by 10 to 20.5 wt %,K₂O by 0.5 to 4 wt % and P₂O₅ by 0 to 5 wt %.

The glass composition may contain B₂O₃ by 0.1 to 12 wt %.

The glass composition may contain B₂O₃ by 0.1 to 12 wt, BaO by 0.1 to4.0 wt %, SrO by 0.1 to 3.5 wt %.

The glass composition may contain B₂O₃ by 0.1 to 12 wt % (provided thatthe KI value is 40 or more).

The glass composition may contain no B₂O₃, and may contain BaO by 0.1 to4.0 wt % and SrO by 0.1 to 3.5 wt %.

SiO₂

If the SiO₂ content is less than 52 wt %, the chemical durability of theglass wool product is unnecessarily degraded, so that the glasscomposition is not suitable for manufacturing inorganic fiber. Inaddition, cullet contains a lot of SiO₂. Thus, if only cullet is used asraw material, generally the SiO₂ content tends to become 52 wt % ormore. If, on the other hand, SiO₂ is contained by more than 75 wt %, theKI value and the solubility to physiological salt water are reduced.Additionally, if the SiO₂ content exceeds 75 wt %, the softening pointof the produced glass composition rises to make it hardly melt and raisethe glass viscosity. Thus, it is difficult to manufacture inorganicfiber from such glass composition.

Al₂O₃

If the Al₂O₃ content is 3 wt % or more, the chemical durability of theinorganic fiber made of the glass composition is raised unnecessarily toby turn remarkably reduce the solubility to physiological salt water.The glass composition may not contain Al₂O₃. Alternatively, it maycontain Al₂O₃ by less than 3 wt %.

CaO and MgO

The glass composition contains CaO by 7.5 to 9.5 wt % and MgO by 0 to 7wt %.

If the CaO content is less than 7.5 wt %, both the solubility of theglass composition to physiological salt water and the liquidustemperature are low, but the glass viscosity becomes too high for theglass composition to be used for manufacturing inorganic fiber.Furthermore, the contents of the ingredients other than CaO areinevitably raised to by turn push up the cost. If the CaO contentexceeds 9.5 wt %, the liquidus temperature is raised, so that the glasscomposition is no longer suitable for manufacturing inorganic fiber.

If the MgO content is 0.1 wt % or more, it can inhibits the glassviscosity and the liquidus temperature from increasing. However, othergradient also inhibits the glass viscosity. Thus, MgO is not essential.If the MgO content exceeds 7 wt %, the glass viscosity becomes too high,so that the glass composition is no longer suitably for manufacturinginorganic fiber.

BaO and SrO

The glass composition contains BaO by 0 to 4 wt % and SrO by 0 to 3.5 wt%. Alternatively, it may contain BaO by 0.1 to 4.0 wt % and SrO by 0.1to 3.5 wt %.

The BaO content increases the bio-solubility of the glass composition.Additionally, both of the BaO content and the SrO content decreases theglass viscosity and the glass softening point of the glass composition,to easily produce inorganic fiber. BaO and SrO do not increase theliquidus temperature unlike BaO, and also do not increase the glassviscosity unlike MgO, so as to easily produce inorganic fiber. For thesereasons, it is preferable to contain BaO and SrO. When BaO by 0.1 wt %and SrO by 0.1 wt % are included, the bio-solubility increases.

However, it should be noted that the bio-solubility, the glassviscosity, the glass softening point and the liquidus temperature arenot determined only by the BaO content, and relate to the contents ofthe other ingredients. Thus, it is not required that BaO is essential.

When the BaO content of the glass composition exceeds 4 wt %, thechemical durability is decreased so that it is no longer suitable formanufacturing inorganic fiber, although the solubility of the glassrelative to physiological salt water is increased.

If the SrO content exceeds 3.5 wt %, the solubility of the glasscomposition to the physiological salt water is decreased.

Na₂O and K₂O

The glass composition contains Na₂O by 10 to 20.5 wt % and K₂O by 0.5 to4 wt %.

If the Na₂O content is below 10 wt %, the solubility of the glasscomposition to physiological salt water becomes too low, and the contentof other ingredients needs to be increased to consequently raise thecost. If, on the other hand, the Na₂O content exceeds 20.5 wt %, thechemical durability of the glass composition is decreased so that thecomposition is no longer suitable for manufacturing inorganic fiber,although the solubility to physiological salt water is increased.

If the K₂O content is below 0.5 wt %, the glass viscosity of the glasscomposition increases to lower the operating efficiency of theglass-fiberizing apparatus. If, on the other hand, K₂O exceeds 4 wt %,the furnace is eroded excessively to shorten the service life of thefurnace and to increase the repairing cost of the furnace. Thus, it willnot be possible to manufacture inorganic fiber at low cost.

P₂O₅

Since P₂O₅ improves the thermal resistance of glass, it operateseffectively when its content is 0.1 wt % or more. However, the thermalresistance of glass can be obtained by some other ingredients, it is notrequired that P₂O₅ is essential. If, the P₂O₅ content exceeds 5 wt %,the bio-solubility of the glass composition is decreased, and the glasssoftening point is too increased, so that the fiberizing is difficult.

B₂O₃

The glass composition contains B₂O₃ by 0 to 12 wt %, preferably, by 0.1to 12 wt %. However, the glass composition may not contain B₂O₃ at all.

B₂O₃ increases the bio-solubility. Thus, it is preferable to containB₂O₃ by 0.1 wt % or more. The bio-solubility is increased when the B₂O₃content is 0.1 wt % or more.

However, the bio-solubility is not determined only by the B₂O₃ content,and relate to the contents of the other ingredients. Thus, it is notrequired that B₂O₃ is essential. Particularly, borax Na₂B₄O₇.nH₂O thatis the raw material of boron oxide is expensive, and the cost ofmanufacturing the glass composition will inevitably be increased if muchborax is used. The present invention aims to increase the bio-solubilityand to decrease the manufacturing cost.

Particularly, when B₂O₃ is not contained and BaO is essential, thebio-solubility of a glass composition is increased by using BaO insteadof costly boron oxide.

When the B₂O₃ content exceeds 12 wt %, the chemical durability would bedecreased, and the manufacturing cost is increased.

Others

In addition to the above ingredients, the glass composition according tothe invention may contain zinc oxide, lithium oxide, zirconium oxide,titanium dioxide, triiron tetraoxide, iron oxide, antimony trioxideand/or lead oxide. These additional ingredients are made to be containedby taking the quality (restoration ratio) of the inorganic fiber and themolded product made of such inorganic fiber derived from the glasscomposition into consideration.

Bio-Solubility and KI Value

The glass composition having the above described composition showsbio-solubility. The expression of “bio-solubility” refers to thesolubility of glass composition to human body fluid. The bio-solubilityis determined by observing the solubility to physiological salt water.If the bio-solubility is high, the inorganic fiber can be easilydissolved into human body fluid. Thus, even if dust of inorganic fiberis inhaled to a lung or chest, it is dissolved into human body fluid, sothat it is eliminated from the human body before it exerts any harmfuleffect on the human body.

The KI value is a reference of the bio-solubility and arithmeticallydetermined from the composition of glass. However, glass containsvarious oxides, and interactions of various oxides may also affect thebio-solubility of glass, so that the KI value is not linearlyproportional to the solubility of glass to physiological salt water. Toprevent inorganic fiber from exerting any harmful effect on the humanbody, the solubility of inorganic fiber to physiological salt water ismainly taken into consideration for the purpose of the invention.

From the viewpoint of harmful effect on the human body, it is desirablethat inorganic fiber shows a high bio-solubility. However, a highbio-solubility means a poor chemical stability. In other words, if theglass composition showing an excessively high bio-solubility, suchinorganic fiber and a molded product thereof can be poorly durable.

The present invention is invented under the consideration of both thebio-solubility and the durability which contradict each other.

While the bio-solubility of the inorganic fiber (or the solubility tophysiological salt water) can vary enormously depending on thecomposition of the glass, it needs to be at least 4.5 wt %. In the caseof the glass composition containing no B₂O₃, the bio-solubility ispreferably 4.5 wt % or more, more preferably 5.59 wt % or more. In thecase of the glass composition containing B₂O₃, the bio-solubility ispreferably 7 wt % or more.

Raw Material

The raw material of the glass composition having the composition asdescribed above may be all cullet, or a cullet with a batch material(feldspar, dolomite, soda ash, borax, etc.). It may be an all batchmaterial.

Cullet to be use for the purpose of the invention may be plate glasscullet or bottle glass cullet. Cullet of glass table ware and/or glassart may be added. Additionally, it is preferable to use cullet ofcathode ray tube glass and/or liquid crystal glass. For the purpose ofthe present invention, cathode ray tube glass is not limited to glassused for television sets, and may be cathode ray tube glass used fordisplays of personal computers. Again, liquid crystal glass is notlimited to glass used for television sets and may be liquid crystalglass used for displays of personal computers. Cathode ray tube glassand liquid crystal glass contain barium oxide BaO and strontium oxideSrO, which prevent the glass softening point and the glass viscosityfrom decreasing and prevent the liquidus temperature from increasing.

Preferably, the material contains cullet of cathode ray tube glassand/or liquid crystal glass by 0 to 50 wt %. If the cullet contentexceeds 50 wt %, the SrO content becomes too high to by turn excessivelyincrease the chemical durability and decrease the bio-solubility.

More preferably, the material contains cullet of cathode ray tube glassand/or liquid crystal glass by 8 to 50 wt %. If the cullet content isless than 8 wt %, BaO and SrO are insufficient. Although the necessaryamount of BaO and SrO can be obtained by adding a batch material, themanufacturing cost will be increased.

The cullet of cathode ray tube glass and/or liquid crystal glass showsan average particle size of 5 to 60 mm. However, the present inventiondoes not exclude the use of cullet showing an average particle size lessthan 5 mm or more than 60 mm.

The use of cullet of cathode ray tube glass and/or liquid crystal glasscontributes to effective recycling of resources, reduce themanufacturing cost of the glass composition, the inorganic fiber and themolded product.

Method of Preparing a Glass Composition According to the Invention

A method as described below may be used to prepare the glasscomposition. The raw materials (namely, plate glass cullet, bottle glasscullet, a batch material and, if necessary, cullet of cathode ray tubeglass and/or liquid crystal glass) are fed to respective silos/storagetanks by means of conveyors and/or air shoots, and stored in them. Then,a necessary amount of each of the raw materials (the cullet and/or thebatch material) is measured by a gauge, and fed to a mixing silo by anair shoot. The metered and transferred raw materials are mixed in themixing silo to prepare the glass composition. The prepared glasscomposition is then transferred to a feed silo arranged in front of aglass melting furnace.

Method of Manufacturing Inorganic Fiber

Glass fiber, glass wool, rock wool and so on can be manufactured fromthe above described glass composition. Particularly, a known techniquesuch as centrifugal method or flame method may be used whenmanufacturing glass wool.

Method of Manufacturing Molded Product of Inorganic Fiber

A molded product of inorganic fiber, glass wool in particular, that canbe used as thermal insulator and sound absorber can be manufactured fromthe inorganic fiber, glass wool in particular.

When manufacturing the glass wool molded product, it is preferable touse an adhesive agent as binder/adhesive in order to maintain the shapeof the molded product and provide the molded product with desired loadcharacteristics. The adhesive agent contains thermosetting resin such asphenol resin that operates as organic binder. Alternatively the adhesiveagent may contain some other thermosetting resin, epoxy or melamine.Still alternatively, an inorganic binder may be used.

The binder/adhesive is blown to fined molten glass to an adhering ratioof about 5%. Any appropriate known blowing method may be used for thepurpose of the invention.

The density of the glass wool molded product is normally between 7 and300 Kg/m3, although it may vary depending on the characteristicsrequired to it when it is used as thermal insulator or sound absorber.

As for the dimensions of the glass wool molded product, it is normally12 to 300 mm of thickness, 260 to 1,100 mm of width and 605 to 22,000 mmof long, although the present invention is by no means limited to thesenumerical values.

If necessary, a facing material may be applied to the surface of theglass wool molded product obtained in a manner as described above. Aknown appropriate material such as a glass cloth, vinyl chloride, anorganic unwoven cloth and so on may be used for the facing material. Thefacing material can be bonded to the surface by any known technique,such as a hot-melt type adhesive or an organic solvent type adhesive.

EXAMPLE 1

A 67.5 wt % of plate glass and bottle glass cullet, a 10 wt % of culletof television set cathode ray tube glass, a 10 wt % of cullet of liquidcrystal glass, and a 12.5 wt % of a batch material were put together,stirred, mixed and molten to obtain a glass composition as shown inTable 1 below. The average particle size of the cullet was 5 to 60 mm.

After cooling, the glass composition was crushed to particles not largerthan 180 microns. A 1 g of the crushed glass was put into a triangularflask. Then, a 150 ml of physiological salt water was poured into theflask, and the flask was left in a warm bath at 40±1° C. for 50 hours.Thereafter, the content of the flask was filtered, and the residue wasweighed to determine the reduced amount, to obtain the solubility. Theobtained result is also shown in Table 1.

The obtained glass composition was molten. The molten glass was forcedto flow out through a large number of holes of a centrifugal fiberizingapparatus, to produce fine filaments as glass wool. The viscosity, thesoftening point and the liquidus temperature of the molten glass arealso shown in Table 1. The viscosity is expressed as the temperaturewhen the glass showed the viscosity of 10,000 poises.

A glass wool molded product and a glass wool thermal insulator wereprepared by using the glass wool obtained in a manner as describedabove. A phenol type adhesive agent (binder) was made to adhere to theglass wool to an adhering ratio of 5% in order to provide it with shapestability and load characteristics. The glass wool with the binder wascollected by a fiber collector, dried, and cut to a piece of 10 kg/m³×50mm×430 mm×1,370 mm to obtain a glass wool molded product.

An aluminum-deposited polyethylene film was bonded to an upper surfaceof the obtained glass wool molded product by means of a hot melt typeadhesive agent, to obtain a glass wool thermal insulator.

The obtained glass wool thermal insulator was compressed to 87% byvolume, and held to the compressed state for 1 month and 3 months, afterthe elapse of each of which the restoration rate was observed. Therestoration rate was obtained by releasing the insulator from thecompressed state, and gauging the thickness of the insulator four hoursthereafter. The obtained restoration ratio is also shown in Table 1.

COMPARATIVE EXAMPLE 1

A glass composition, glass wool and a glass wool thermal insulator wereprepared by following the process of Example 1 except that thecomposition as shown in Table 1 was obtained by using a 70 wt % of flatglass and bottle glass cullet and a 30 wt % of a batch material as rawmaterial.

Example 1 and Comparative Example 1 will be compared each other anddiscussed. In Example 1, cullet of cathode ray tube glass of televisionsets and liquid crystal glass were added. Thus, the content of aluminumoxide is low while the products of Example 1 contained BaO and SrO thatwere derived from the cathode ray tube glass and the liquid crystalglass.

The solubility of the glass composition of Example 1 is higher than thatof the glass composition of Comparative Example 1 by 33%. In otherwords, the bio-solubility of the glass composition of Example 1 wasremarkable improved.

Additionally, the viscosity of Example 1 was largely improved by 40° C.,and the softening point of Example 1 was also largely improved by 35°C., so as to easily fiberize the glass.

EXAMPLE 2

A glass composition, glass wool and a glass wool thermal insulator wereprepared by following the process of Example 1 except that thecomposition as shown in Table 1 was obtained by using a 62 wt % of plateglass and bottle glass cullet, a 21 wt % of cullet of cathode ray tubeglass of television sets and a 17 wt % of a batch material as rawmaterial.

The solubility of Example 2 showed a remarkable improvement relative tothat of Comparative Example 1.

EXAMPLE 3

A glass composition, glass wool and a glass wool thermal insulator wereprepared by following the process of Example 1 except that thecomposition as shown in Table 1 was obtained by using a 72.7% of plateglass and bottle glass cullet, a 10 wt % of cullet of cathode ray tubeglass of television sets, and a 17.3 wt % of a batch material as rawmaterial.

The solubility of Example 3 showed an improvement relative to that ofComparative Example 1.

When manufacturing glass wool in Example 3, the temperature at 10,000poises was 925° C., and the liquidus temperature was as low as 915° C.,so as to easily fiberize the glass. In other words, the glasscomposition of Example 3 was found to be suitable for manufacturinginorganic fiber.

Additionally, the restoration ratio of the glass wool thermal insulatorprepared from the glass composition of Example 3 was 120% after theelapse of a month and 116% after the elapse of 3 months, to prove aremarkable improvement relative to 118% after the elapse of a month and112% after the elapse of 3 months in Comparative Example 1. Therestoration ratio greatly influences the thickness of the product whenthe packed product is unpacked, and also the touch and the flexibility(resiliency) of the unpacked product. The glass wool thermal insulatormanufactured from the glass composition of Example 3 showed a remarkablyimproved quality, to prove that the glass composition of Example 3 isvery suited to molded products of inorganic fiber. TABLE 1 Compar- ativeExample Example Example 1 Example 1 2 3 RAW MATERIAL (wt %) flat/bottleglass cullet 67.5 70.0 62.0 72.7 cullet of CRT glass 10.0 0 21.0 10.0cullet of liquid crystal 10.0 0 0 0 glass batch material 12.5 30.0 17.017.3 GLASS COMPOSITION (wt %) SiO₂ 58.32 62.61 59.49 62.72 Al₂O₃ 2.684.03 2.08 2.69 CaO 8.01 7.33 8.80 7.79 MgO 3.35 2.67 1.95 1.13 Na₂O17.41 14.77 15.28 14.64 K₂O 1.17 2.45 2.09 1.88 Fe₂O₃ 0.475 0.725 0.4660.153 B₂O₃ 2.64 4.71 0.89 4.34 BaO 2.38 0 2.21 0.95 SrO 1.68 0 2.01 1.30P₂O₅ 1.35 0 1.01 1.18 others 0.535 0.705 0.724 1.227 KI value 29.6023.87 28.35 25.35 solubility (wt %) 7.591 5.717 6.676 6.450 viscosity (°C.) 885 925 905 925 softening point (° C.) 615 650 630 650 liquidustemperature 915 915 910 915 (° C.) product restoration ratio after 1month 117% 118% 118% 120% after 3 months 111% 112% 112% 116%

EXAMPLE 4

A glass composition, glass wool and a glass wool thermal insulator wereprepared by following the process of Example 1 except that thecomposition as shown in Table 2 was obtained by using a 90% of plateglass and bottle glass cullet and a 10 wt % of cullet of cathode raytube glass of television sets as raw material. The obtained results areshown in Table 2 below.

Note that both the glass composition of Example 4 and that ofComparative Example 2, which will be described hereinafter, do notcontain B₂O₃. Thus, the KI values thereof were determined by subtractingtwice of the content of oxides of aluminum from the content (wt %) ofthe oxides of sodium, potassium, calcium, magnesium and barium.

COMPARATIVE EXAMPLE 2

Comparative Example 2 shows that the bio-solubility is improved when BaOand SrO are contained, if compared with Example 4.

A glass composition, glass wool and a glass wool thermal insulator wereprepared by following the process of Example 1 except that thecomposition as shown in Table 2 was obtained by using a 100% of plateglass and bottle glass cullet as raw material. The obtained results areshown in Table 2 below. TABLE 2 Comparative Example 4 Example 2 RAWMATERIAL (wt %) flat/bottle glass cullet 90.0 100.0 cullet of CRT glass10.0 GLASS COMPOSITION (wt %) SiO₂ 70.23 70.28 Al₂O₃ 1.72 1.76 CaO 8.388.84 MgO 2.75 2.92 Na₂O 13.52 13.98 K₂O 1.21 0.68 Fe₂O₃ 0.747 0.881 BaO0.45 SrO 0.46 others 0.533 0.659 KI value 22.87 22.90 solubility (wt %)5.591 5.578 viscosity (° C.) 1034 1035 softening point (° C.) 725 725liquidus temperature(° C.) 1010 1040 product restoration ratio after 1month 118% 117% after 3 months 116% 115%

In the Example 4 and the Comparative Example 2, contained B₂O₃ was notcontained. Thus, they showed a low bio-solubility if compared withExamples 1-3 and Comparative Example 1. However, it will be appreciatedthat the bio-solubility of Example 4 is improved if compared with thatof Comparative Example 2. It will be safe to assume that thisimprovement is derived from the barium oxide contained in the cullet ofcathode ray tube glass.

What is more important is that the liquidus temperature of Example 4 wasmade lower than that of Comparative Example 2 by 30° C., so as to easilymake inorganic fiber (fiberization). It may be safe to assume that thiseffect is derived from the barium oxide contained in the cathode raytube glass, and barium oxide has an effect of preventing the liquidustemperature from rising.

In the Comparative Example 2, the glass showed 10000 poises at 1035° C.,and the liquidus temperature was 1040° C. which was higher than 1035° C.Thus, it was difficult to fiberize the glass in the Comparative Example2. On the other hand, in the Example 4, although the glass showed 10000poises at 1034° C. which was similar to the viscosity in ComparativeExample 2, the liquidus temperature was 1010° C. which was low. Thus, inthe Example 4, the glass was easily fiberized. In other words, the glasscomposition of Example 4 was found to be suitable for manufacturinginorganic fiber if compared with the glass composition of ComparativeExample 2.

The restoration ratio of the glass wool thermal insulator manufacturedaccording to Example 4 was better than that according to ComparativeExample, 2 to evidence that the glass wool thermal insulator of Example4 had a better quality. It may be safe to assume that this is derivedfrom the strontium oxide contained in the cathode ray tube glass, whichcan improve the durability like aluminum oxide.

Unlike Examples 1-3, the glass composition of Example 4 did not containB₂O₃ at all, but showed a numerical mechanical durability substantiallysame as those of the other examples. Thus, it was confirmed that theglass composition of Example 4 is suitable for manufacturing a moldedproduct of inorganic fiber.

EXAMPLES 5-7

Glass wool and a molded product of glass wool were prepared by followingthe process of Example 1 except that a 57.0% of plate glass and bottleglass cullet, a 10.6 wt % of cullet of cathode ray tube glass oftelevision sets and a 32.4 wt % of a batch material were used as rawmaterial in Example 5, a 56.0% of plate glass and bottle glass cullet, a12.0 wt % of cullet of liquid crystal glass and a 32.0 wt % of a batchmaterial were used as raw material in Example 6, and a 59% of plateglass and bottle glass cullet and a 41 wt % of a batch material wereused as raw material in Example 7. The ingredients were put together,stirred and mixed to obtain the respective glass compositions as listedin Table 3. TABLE 3 Example 5 Example 6 Example 7 RAW MATERIAL (wt %)flat/bottle glass cullet 57.0 56.0 59.0 cullet of CRT glass 10.6 culletof liquid crystal glass 12.0 batch material 32.4 32.0 41.0 GLASSCOMPOSITION (wt %) SiO₂ 52.35 53.49 56.00 Al₂O₃ 1.30 1.50 1.05 CaO 8.809.10 9.00 MgO 2.07 3.40 2.06 Na₂O 18.80 19.20 19.34 K₂O 1.45 0.51 0.70Fe₂O₃ 0.122 0.613 0.126 B₂O₃ 10.50 10.50 11.00 BaO 1.09 0.33 0 SrO 1.500.20 0 P₂O₅ 1.15 0 0 others 0.868 1.157 0.724 KI value 40.11 40.04 40.00solubility (wt %) 25.097 25.033 24.913 viscosity (° C.) 835 835 830softening point (° C.) 565 565 560 liquidus temperature(° C.) 913 915920 product restoration ratio after 1 month 116% 115% 115% after 3months 111% 111% 111%

The solubility values of Examples 5-7 were very high. Although thechemical durability may be lowered by a high solubility, the SrO contentof Example 5 and that of Example 6 prevent the chemical durability fromdecreasing excessively.

While a raw material containing cullet of cathode ray tube glass or thatof liquid crystal glass was used in Example 5 and 6, the raw material ofExample 7 contained neither cullet of cathode ray tube glass nor that ofliquid crystal glass. While not only the solubility but also thesoftening point, the liquidus temperature, the solubility and therestoration rate of the product were similar in Examples 5-7, the glasscomposition manufacturing cost of Example 5 and that of Example 6 wereas low as about two thirds of the glass composition manufacturing costof Example 7, because cullet of cathode ray tube glass or that of liquidcrystal glass was used in the former examples. In other words, theseexamples evidenced that the use of cullet of cathode ray tube glassand/or that of liquid crystal glass can significantly reduce themanufacturing cost. While the solubility in each of Examples 5-7 wasvery high, the glass composition manufacturing cost was about 200%higher than that of any of Examples 1-4.

According to the present invention, since the glass composition hasspecifically defined contents of ingredients (contains SiO₂ by 52 to 72wt %, Al₂O₃ by less than 3 wt %, MgO by 0 to 7 wt %, CaO by 7.5 to 9.5wt %, B₂O₃ by 0 to 12 wt, BaO by 0 to 4 wt %, SrO by 0 to 3.5 wt %, Na₂Oby 10 to 20.5 wt %, K₂O by 0.5 to 4.0 wt % and P₂O₅ by 0 to 5 wt %), thebio-solubility is improved, and has a desired level of chemicaldurability. Also, the glass viscosity, the glass softening point and theliquidus temperature thereof are reduced, so as to easily fiberize theglass. Therefore, according to the invention, there is provided theglass composition to be used for manufacturing inorganic fiber at lowcost.

In addition to the above described advantages, there is provided theglass composition showing a high bio-solubility, if B₂O₃, which improvesbio-solubility, is essential.

If B₂O₃, BaO and SrO are essential, there is provided the glasscomposition which liquidus temperature, glass softening point and glassviscosity are decreased, so as to easily fiberize the glass.Additionally, since BaO is essential, its bio-solubility is increased.

If P₂O₅ is essential, the thermal resistance is improved in addition tothe above.

If B₂O₃ is essential and has KI value of 40 or more, there is providedthe glass composition with a very high bio-solubility.

If BaO and SrO are essential instead of B₂O₃, the liquidus temperature,the glass softening point and the glass viscosity are decreased, so asto easily fiberize the glass. In addition, BaO is essential, itsbio-solubility is accordingly increased.

If the raw material of the glass composition contains cathode ray tubeglass and/or liquid crystal glass by 0 to 50 wt %, cullet of cathode raytube glass and that of liquid crystal glass can be effectively used asresources, and the glass composition can be obtained without difficultybecause of BaO and SrO contained in them.

Finally, the manufacturing cost can be reduced, if the raw materialcontains cullet of cathode ray tube glass and/or that of liquid crystalglass.

1. A glass composition to be used for manufacturing inorganic fiber,containing SiO₂ by 52 to 72 wt %, Al₂O₃ by less than 3 wt %, MgO by 0 to7 wt %, CaO by 7.5 to 9.5 wt %, B₂O₃ by 0 to 12 wt, BaO by 0 to 4 wt %,SrO by 0 to 3.5 wt %, Na₂O by 10 to 20.5 wt %, K₂O by 0.5 to 4.0 wt %and P₂O₅ by 0 to 5 wt %.
 2. The glass composition according to claim 1,containing B₂O₃ by 0.1 to 12 wt %.
 3. The glass composition according toclaim 2, containing BaO by 0.1 to 4.0 wt % and SrO by 0.1 to 3.5 wt %.4. The glass composition according to claim 3, containing P₂O₅ by 0.1 to5 wt %.
 5. The glass composition according to claim 1, containing B₂O₃by 0.1 to 12 wt %, and having KI value of 40 or more, said KI valuebeing obtained by formulaKI=(Na₂O+K₂O+CaO+MgO+BaO+B₂O₃)−2×Al₂O₃, where the molecular formulasrepresents the respective contents expressed by wt %.
 6. The glasscomposition according to claim 1, containing BaO by 0.1 to 4 wt %, SrOby 0.1 to 3.5 wt %, but not containing B₂O₃.
 7. The glass compositionaccording to one of claims 1-6, wherein raw material of the glasscomposition contains cathode ray tube glass and/or liquid crystal glassby 0 to 50 wt %.
 8. The glass composition according to one of claims1-6, wherein raw material of the glass composition contains cathode raytube glass and/or liquid crystal glass by 8 to 50 wt %.
 9. A method ofmanufacturing a molded product of inorganic fiber, comprising: meltingthe glass composition according to one of claims 1-8 in a meltingfurnace; fining the molten glass composition into fine glass fiber in afiberizing apparatus; blowing an adhesive agent (binder) to the glassfiber to provide it with shape stability and load characteristics;molding the glass fiber into the inorganic fiber molding having apredetermined density and a predetermined thickness by means of a fibercondenser and a dryer; and subsequently cutting the molding to produce afinished product.
 10. A molded product of inorganic fiber manufacturedby the method according to claim 9.